Financing a car/motorcycle

I just need somebody to help me understand why in Texas when I go to a dealership to finance a car the year I look at is 2018-2020+ I can put down $500-2,000 with around 700+ of credit a job is a swing and a miss but I do have now a really good job and a very good paying one but still was denied I haven’t bought or financed a vehicle on apps like Carvana,carmaxx etc but I did buy a 04 Honda civic ex that was a private seller and a vitacci 250cc motorcycle but they tell me I need a co-signer since I’m new to buying/financing do I need to go lower with the year or am I doing something wrong or overlooking something?